Hydrogen peroxide (H₂O₂) is considered as one of the most important green oxidants for a wide range of industries, including wastewater treatment, papermaking and green chemical synthesis etc. On site production of H₂O₂ via two electron oxygen reduction reaction (2e-ORR) process has attracted enormous attention in the fields of green chemistry, chemical engineering, environmental and material science. Scientists from Energy Catalysis & Materials group in Shenyang National Laboratory for Materials Science (SYNL) have made new progress in highly efficient hydrogen peroxide electrosynthesis with nano-carbon as catalytic materials.

The research team leading by Dr. Wei Qi firstly revealed that the active sites for 2e-ORR could be attributed to carboxyl and carbonyl groups on nanocarbon catalysts via linking the catalytic activity with the accurate chemical composition and structure of nano-carbon materials. The detailed kinetic analysis indicated that the key for the selectivity of 2e/4e-electron product is the adsorption/desorption strength between the active sites of carboxylic groups and H₂O₂.

Following these fundamental understandings on the catalytic process and corresponding structure-function relations, Dr. Wei Qi and co-workers have developed a novel carbon/surfactant composite electrode for highly selective hydrogen peroxide electrosynthesis with cooperations with research teams from Peking University and Fuzhou University. The system was designed based on the principle of surface engineering and kinetic modulation without changing the surface chemical properties of the carbon catalyst, and the important role of the cationic surfactant is to weaken the interactions between carboxyl active sites and H₂O₂, thus promoting the efficiency and stability for H₂O₂ electrosynthesis. In alkaline media, a sustainably high selectivity of peroxide (>96%) across the potential window over 0.8 V for over 10 h could be achieved with the proposed carbon/surfactant system, which outperforms typical noble metal catalysts becoming the new record for H₂O₂ electrocatalysts.

These findings are anticipated to highlight the importance of interface design in electrocatalytic reaction systems and to provide mechanistic insight for advancing the potential practical applications of H₂O₂ electrosynthesis. These serial research works are published in Journal of Colloid and Interface Sciences (active sites identification and quantification) and Chem (kinetics and surface engineering). Miss Xingyu Lu and Dr. Kuang-Hsu Wu from Energy Catalysis & Materials group are first authors for these two papers, respectively. The authors acknowledge the financial support from NSFC, the Youth Innovation Promotion Association and SYNL.

Fig. 1 In-situ selectivity modulation by surface-acting cations at the carbon surface.

Fig. 2 (a) Two-electron selectivity and oxygen content for different carbon materials: kinetic fitting and experimental measurements.

Fig. 3 Selectivity performance of the proposed carbon/surfactant (CTAB) system: comparisons of peroxide selectivity and potential window width among reported electrocatalyst systems.

Fig. 4 Surface oxygen chemistry of the proposed carbon/surfactant (CTAB) system: XPS O1s spectra and NEXAFS C and O K-edge spectra before and after ORR.

Fig. 5 The kinetic model analysis of carbonyl and carboxyl functionalities.